Rechargeable lithium-ion batteries with high energy density and long cycle life are increasingly needed for applications ranging from portable electronics to electric vehicles and smart grids. To meet these demands, researchers have been exploring high-capacity anode materials that operate through conversion and/or alloying reactions. These materials can store far more lithium than conventional graphite anodes, but they also face major challenges during battery operation.
One particularly puzzling issue is a phenomenon known as activation. In many high-capacity anodes, battery capacity initially drops and only gradually recovers over repeated charge-discharge cycles. This process delays full capacity utilization and can compromise the structural integrity of the electrode. Although activation has been widely observed in high-capacity materials, its origin has remained unclear.
The research team led by Prof. Fangxi Xie and Mingmei Wu at Sun Yat-sen University , China, in collaboration with Dr. Shengfu Tong from Jinhua Advanced Research Institute, China, and Prof. David Kisailus from the University of California, Irvine, USA, systematically revealed the origin of the activation process in high-capacity lithium-ion battery materials and elucidated its underlying size-dependent mechanism. Their findings show that particle size plays a decisive role in determining whether activation occurs.
The team published their research in Nano Research on July 2, 2026.
They found that electrodes made of large particles (~500 nm) exhibited pronounced activation behavior during cycling, whereas electrodes made of small particles (~65 nm) showed little to no activation. By tracking the evolution of characteristic elements at different cycling stages, the researchers discovered that lithiation proceeds very differently in the two systems. In small-particle electrodes, electrolyte can rapidly penetrate and facilitate lithiation. In contrast, large-particle electrodes require substantially more time for the electrolyte to fully access the active material.
To understand the origin of this size dependence, the researchers combined experimental observations with finite-element simulations and electrochemical kinetic analyses. They found that the distinct activation behaviors arise from a stress-induced retardation effect associated with a core-shell lithiation mode. During the lithiation of larger particles, compressive stress accumulates in the lithiated outer shell, hindering lithium transport and delaying the inward lithiation. This stress-induced kinetic retardation gives rise to the prolonged activation behavior observed in large-particle electrodes. In contrast, the stress effect is much less pronounced in smaller particles, allowing lithiation to proceed more easily and enabling stable cycling with little to no activation.
The findings provide a new mechanistic understanding of activation in high-capacity lithium-ion anodes and suggest practical strategies for improving battery performance. By tailoring particle size and controlling lithiation kinetics, it may be possible to reduce or even avoid activation, accelerate full capacity utilization, and improve the cycling stability of advanced battery materials.
Other contributors include Shuting Fu, Shiman He, Xuxu Wang, Xiaohui Li, and Junyu Hong from Sun Yat-sen University, China.
This work was supported by the National Natural Science Foundation of China (NSFC) (Nos. 22405297, 51672315, U1801251 and 21403106), the talent recruitment project of Guangdong (No. 2023QN10C330), the Multi-University Research Initiative (AFOSR-FA9550-15-1-0009) and the Winston Chung Global Energy Center.
DOI Link:
https://doi.org/10.26599/NR.2026.94908669
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 8,000 articles. In 2025 InCites Journal Citation Reports, its 2025 IF is 9.4 (8.3, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.
